/*
This file is part of Ext JS 4.2

Copyright (c) 2011-2013 Sencha Inc

Contact:  http://www.sencha.com/contact

GNU General Public License Usage
This file may be used under the terms of the GNU General Public License version 3.0 as
published by the Free Software Foundation and appearing in the file LICENSE included in the
packaging of this file.

Please review the following information to ensure the GNU General Public License version 3.0
requirements will be met: http://www.gnu.org/copyleft/gpl.html.

If you are unsure which license is appropriate for your use, please contact the sales department
at http://www.sencha.com/contact.

Build date: 2013-03-11 22:33:40 (aed16176e68b5e8aa1433452b12805c0ad913836)
*/
/**
 * @class Ext.data.JsonP
 * @singleton
 * This class is used to create JSONP requests. JSONP is a mechanism that allows for making
 * requests for data cross domain. More information is available <a href="http://en.wikipedia.org/wiki/JSONP">here</a>.
 */
Ext.define('Ext.data.JsonP', {

    /* Begin Definitions */

    singleton: true,

    /* End Definitions */

    /**
     * Number of requests done so far.
     * @private
     */
    requestCount: 0,

    /**
     * Hash of pending requests.
     * @private
     */
    requests: {},

    /**
     * @property timeout
     * @type Number
     * A default timeout for any JsonP requests. If the request has not completed in this time the
     * failure callback will be fired. The timeout is in ms. Defaults to <tt>30000</tt>.
     */
    timeout: 30000,

    /**
     * @property disableCaching
     * @type Boolean
     * True to add a unique cache-buster param to requests. Defaults to <tt>true</tt>.
     */
    disableCaching: true,

    /**
     * @property disableCachingParam
     * @type String
     * Change the parameter which is sent went disabling caching through a cache buster. Defaults to <tt>'_dc'</tt>.
     */
    disableCachingParam: '_dc',

    /**
     * @property callbackKey
     * @type String
     * Specifies the GET parameter that will be sent to the server containing the function name to be executed when
     * the request completes. Defaults to <tt>callback</tt>. Thus, a common request will be in the form of
     * url?callback=Ext.data.JsonP.callback1
     */
    callbackKey: 'callback',

    /**
     * Makes a JSONP request.
     * @param {Object} options An object which may contain the following properties. Note that options will
     * take priority over any defaults that are specified in the class.
     * <ul>
     * <li><b>url</b> : String <div class="sub-desc">The URL to request.</div></li>
     * <li><b>params</b> : Object (Optional)<div class="sub-desc">An object containing a series of
     * key value pairs that will be sent along with the request.</div></li>
     * <li><b>timeout</b> : Number (Optional) <div class="sub-desc">See {@link #timeout}</div></li>
     * <li><b>callbackKey</b> : String (Optional) <div class="sub-desc">See {@link #callbackKey}</div></li>
     * <li><b>callbackName</b> : String (Optional) <div class="sub-desc">The function name to use for this request.
     * By default this name will be auto-generated: Ext.data.JsonP.callback1, Ext.data.JsonP.callback2, etc.
     * Setting this option to "my_name" will force the function name to be Ext.data.JsonP.my_name.
     * Use this if you want deterministic behavior, but be careful - the callbackName should be different
     * in each JsonP request that you make.</div></li>
     * <li><b>disableCaching</b> : Boolean (Optional) <div class="sub-desc">See {@link #disableCaching}</div></li>
     * <li><b>disableCachingParam</b> : String (Optional) <div class="sub-desc">See {@link #disableCachingParam}</div></li>
     * <li><b>success</b> : Function (Optional) <div class="sub-desc">A function to execute if the request succeeds.</div></li>
     * <li><b>failure</b> : Function (Optional) <div class="sub-desc">A function to execute if the request fails.</div></li>
     * <li><b>callback</b> : Function (Optional) <div class="sub-desc">A function to execute when the request
     * completes, whether it is a success or failure.</div></li>
     * <li><b>scope</b> : Object (Optional)<div class="sub-desc">The scope in
     * which to execute the callbacks: The "this" object for the callback function. Defaults to the browser window.</div></li>
     * </ul>
     * @return {Object} request An object containing the request details.
     */
    request: function(options) {
        options = Ext.apply({}, options);

        //<debug>
        if (!options.url) {
            Ext.Error.raise('A url must be specified for a JSONP request.');
        }
        //</debug>

        var me = this,
            disableCaching = Ext.isDefined(options.disableCaching) ? options.disableCaching : me.disableCaching,
            cacheParam = options.disableCachingParam || me.disableCachingParam,
            id = ++me.requestCount,
            callbackName = options.callbackName || 'callback' + id,
            callbackKey = options.callbackKey || me.callbackKey,
            timeout = Ext.isDefined(options.timeout) ? options.timeout : me.timeout,
            params = options.params || {},
            url = options.url,
            name = Ext.name,
            request,
            script;


        // Add cachebuster param unless it has already been done
        if (disableCaching && !params[cacheParam]) {
            params[cacheParam] = new Date().getTime();
        } else {
            params = options.params;
        }

        params[callbackKey] = name + '.data.JsonP.' + callbackName;
        script = me.createScript(url, params, options);

        me.requests[id] = request = {
            url: url,
            params: params,
            script: script,
            id: id,
            scope: options.scope,
            success: options.success,
            failure: options.failure,
            callback: options.callback,
            callbackKey: callbackKey,
            callbackName: callbackName
        };

        if (timeout > 0) {
            request.timeout = setTimeout(Ext.bind(me.handleTimeout, me, [request]), timeout);
        }

        me.setupErrorHandling(request);
        me[callbackName] = Ext.bind(me.handleResponse, me, [request], true);
        me.loadScript(request);
        return request;
    },

    /**
     * Abort a request. If the request parameter is not specified all open requests will
     * be aborted.
     * @param {Object/String} request (Optional) The request to abort
     */
    abort: function(request){
        var me = this,
            requests = me.requests,
            key;

        if (request) {
            if (!request.id) {
                request = requests[request];
            }
            me.handleAbort(request);
        } else {
            for (key in requests) {
                if (requests.hasOwnProperty(key)) {
                    me.abort(requests[key]);
                }
            }
        }
    },

    /**
     * Sets up error handling for the script
     * @private
     * @param {Object} request The request
     */
    setupErrorHandling: function(request){
        request.script.onerror = Ext.bind(this.handleError, this, [request]);
    },

    /**
     * Handles any aborts when loading the script
     * @private
     * @param {Object} request The request
     */
    handleAbort: function(request){
        request.errorType = 'abort';
        this.handleResponse(null, request);
    },

    /**
     * Handles any script errors when loading the script
     * @private
     * @param {Object} request The request
     */
    handleError: function(request){
        request.errorType = 'error';
        this.handleResponse(null, request);
    },

    /**
     * Cleans up anu script handling errors
     * @private
     * @param {Object} request The request
     */
    cleanupErrorHandling: function(request){
        request.script.onerror = null;
    },

    /**
     * Handle any script timeouts
     * @private
     * @param {Object} request The request
     */
    handleTimeout: function(request){
        request.errorType = 'timeout';
        this.handleResponse(null, request);
    },

    /**
     * Handle a successful response
     * @private
     * @param {Object} result The result from the request
     * @param {Object} request The request
     */
    handleResponse: function(result, request){

        var success = true;

        if (request.timeout) {
            clearTimeout(request.timeout);
        }
        delete this[request.callbackName];
        delete this.requests[request.id];
        this.cleanupErrorHandling(request);
        Ext.fly(request.script).remove();

        if (request.errorType) {
            success = false;
            Ext.callback(request.failure, request.scope, [request.errorType]);
        } else {
            Ext.callback(request.success, request.scope, [result]);
        }
        Ext.callback(request.callback, request.scope, [success, result, request.errorType]);
        Ext.EventManager.idleEvent.fire();
    },

    /**
     * Create the script tag given the specified url, params and options. The options
     * parameter is passed to allow an override to access it.
     * @private
     * @param {String} url The url of the request
     * @param {Object} params Any extra params to be sent
     * @param {Object} options The object passed to {@link #request}.
     */
    createScript: function(url, params, options) {
        var script = document.createElement('script');
        script.setAttribute("src", Ext.urlAppend(url, Ext.Object.toQueryString(params)));
        script.setAttribute("async", true);
        script.setAttribute("type", "text/javascript");
        return script;
    },

    /**
     * Loads the script for the given request by appending it to the HEAD element. This is
     * its own method so that users can override it (as well as {@link #createScript}).
     * @private
     * @param request The request object.
     */
    loadScript: function (request) {
        Ext.getHead().appendChild(request.script);
    }
});
